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United States Patent |
6,110,759
|
Konrad
,   et al.
|
August 29, 2000
|
Composite structure with a growth substrate having a diamond layer and a
plurality of microelectronic components, and process for producing such
a composite structure
Abstract
A method for producing a composite structure for microelectronic devices
includes producing several microelectronic devices by means of a
deposition method, pre-seeding a surface with growth seeds for a diamond
and depositing the diamond layer from a gas phase. The diamond layer is
provided with thin spots between the devices. According to the invention,
the devices are laid down initially on a growth substrate directly and/or
with the use of the material of the growth substrate. Following the
deposition of the devices, the latter are seeded on their free surfaces
for the diamond layer. The diamond layer is located on the seeded free
surfaces of the devices.
Inventors:
|
Konrad; Brigitte (Blaustein, DE);
Guettler; Herbert (Elchingen, DE)
|
Assignee:
|
DaimlerChrysler AG (Stuttgart, DE)
|
Appl. No.:
|
070853 |
Filed:
|
May 1, 1998 |
Foreign Application Priority Data
| May 02, 1997[DE] | 197 18 618 |
Current U.S. Class: |
438/105; 257/77; 257/E21.125; 257/E27.001 |
Intern'l Class: |
H01L 021/00 |
Field of Search: |
438/105
257/77
|
References Cited
U.S. Patent Documents
5006914 | Apr., 1991 | Beetz, Jr. | 257/77.
|
5082522 | Jan., 1992 | Purdes et al. | 438/641.
|
5087959 | Feb., 1992 | Omori et al.
| |
5204210 | Apr., 1993 | Jansen et al. | 438/198.
|
5358596 | Oct., 1994 | Cappeli et al. | 117/99.
|
5994160 | Nov., 1999 | Niedermann et al. | 438/53.
|
Foreign Patent Documents |
0 589 678 A2 | Mar., 1994 | EP.
| |
44 27 715 C1 | Feb., 1996 | DE.
| |
63-308324 | Dec., 1988 | JP.
| |
5-58784 | Mar., 1993 | JP.
| |
5-114729 | May., 1993 | JP.
| |
5-271939 | Oct., 1993 | JP.
| |
7-101798 | Apr., 1995 | JP.
| |
9-25195 | Jan., 1997 | JP.
| |
WO 92/05110 | Apr., 1992 | WO.
| |
Primary Examiner: Niebling; John F.
Assistant Examiner: Murphy; John
Attorney, Agent or Firm: Evenson, McKeown, Edwards & Lenahan, P.L.L.C.
Claims
What is claimed is:
1. A method for producing a composite structure, comprising:
pretreating a growth substrate;
placing said pretreated growth substrate in a reactor;
depositing a plurality of microelectronic devices on the pretreated growth
substrate to form a substrate;
seeding a surface of the devices facing away from the growth substrate with
growth seeds for depositing a diamond layer, wherein the surface facing
away from the growth substrate is a substrate surface;
precipitating the diamond layer from a gas phase on the substrate surface
of the devices,
wherein the diamond layer comprises a plurality of separate diamond
islands, each diamond island associated with a device in an area above
said device,
wherein each diamond island comprises diamond regions that are spatially
separated from one another, and
wherein the diamond layer has thin spots between the devices.
2. The method according to claim 1, wherein said seeding comprises:
applying a diamond powder in the form of a sludge with a grain diameter up
to 200 .mu.m; and
rubbing or polishing the grains of the diamond powder into substrate
surface.
3. The method according to claim 1, wherein said seeding comprises:
applying a liquid containing diamond grains to the substrate surface; and
exposing the liquid to ultrasound.
4. The method according to claim 1, wherein said seeding comprises:
applying a diamond powder as a sludge with preferably a grain diameter of
up to 200 .mu.m to substrate surface;
rubbing or polishing the grains of the diamond powder into the substrate
surface; applying a liquid to the substrate surface that contains grains
of diamond; and
exposing the liquid to ultrasound.
5. The method according to claim 1, wherein the substrate surface is seeded
selectively.
6. The method according to claim 1, further comprising, prior to said
seeding:
applying an immunization layer to a portion of the substrate surface making
diamond nucleation difficult;
providing growth seeds in an area outside the immunization layer for the
diamond layer; and
removing the immunization layer before or during said precipitating of the
diamond layer.
7. The method according to claim 1, further comprising, following said
seeding:
applying an immunization layer to a portion of the substrate surface making
diamond nucleation difficult;
seeding the substrate surface in an area outside the immunization layer,
mechanically or by using sound on a liquid containing growth seed; and
removing the immunization layer before or during the precipitating of the
diamond layer.
8. The method according to claim 1, further comprising:
providing a portion of the substrate surface with an immunization layer
that makes diamond nucleation difficult;
seeding the device surfaces in the area outside the immunization layer,
wherein the seeding is performed mechanically or by exposing a liquid
containing growth seeds to ultrasound; and
precipitating diamond by a gas phase.
9. The method according to claim 1, wherein the precipitating of the
diamond layer is by an arcjet method.
10. The method according to claim 1, wherein the diamond layer is
precipitated using a plasma-CVD method at temperatures below 450.degree.
C.
11. The method according to claim 1, wherein said precipitating of the
diamond layer is by an arcjet method, wherein said arcjet method
comprises:
igniting a gas to produce an inert plasma;
introducing H.sub.2 into the inert gas plasma during a transitional phase;
and
igniting H.sub.2 and using it as a plasma material, wherein the inert gas
is removed following the transitional phase.
12. The method according to claim 11, further comprising flowing oxygen
together with a gas that is a precursor material into the reactor.
13. The method according to claim 11, further comprising, before igniting
the plasma material:
covering the seeded substrate surface with a cover to protect it against
the plasma material or against a gas stream of a precursor material that
produces a coating action with diamond; and
removing the cover after stabilization of the plasma material or of the gas
stream.
14. The method according to claim 13, wherein said covering is maintained
between 5 and 30 minutes, preferably between 10 and 20 minutes, and more
preferably for approximately 15 minutes.
15. The method according to claim 13, further comprising cooling the cover
at least during the covering of the substrate, preferably by traversing
the cover with a liquid coolant.
16. The method according to claim 1, wherein the substrate is kept at a
temperature during the precipitating of the diamond layer less than
450.degree. C.
17. The method according to claim 4, wherein said liquid contains grains of
diamond with a grain diameter up to 200 .mu.m.
18. The method according to claim 10, wherein the temperature is below
350.degree. C.
19. The method according to claim 10, wherein the temperature is below
300.degree. C.
20. The method according to claim 11, wherein said gas is a noble gas.
21. The method according to claim 11, wherein said gas is argon.
22. The method according to claim 16, wherein the substrate is kept at a
temperature during the precipitating of the diamond layer less than
350.degree. C.
23. The method according to claim 16, wherein the substrate is kept at a
temperature during the precipitating of the diamond layer less than
300.degree. C.
24. The method according to claim 1, wherein said microelectronic devices
are selected from the group consisting of diodes, transistors, capacitors,
inductances, integrated circuits, amplifiers, and storage devices.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German patent 197 18 618.1-33,
filed on May 2, 1997 in Germany, the disclosure of which is expressly
incorporated by reference herein.
The invention relates to a composite structure with a growth substrate
having several microelectronic devices and a diamond layer and a method
for producing the composite structure.
DE 44 27 715 C1 teaches a method for producing a composite substrate in
which a diamond layer is initially deposited directly on a growth
substrate. A semiconductor layer is then placed on the diamond layer.
Several microelectronic devices are then placed on the semiconductor layer
or with the functional assistance of the semiconductor layer. The devices
are to be construed as individual devices such as diodes, transistors,
capacitors, inductances, etc. but also include device groups such as
integrated circuits (ICs), amplifiers, storage devices, etc. As the
semiconductor layer grows, the number of impurities under the devices,
namely in the area of the device root, is reduced. The diamond layer has
edges outside the device roots. On these edges located between the
devices, and on which the diamond layer is thinner than in the vicinity of
the device roots, the quality of the semiconductor layer deposited
subsequently is improved above the diamond layer. Because of this
improvement in semiconductor layer quality, at least in the area of the
device roots, the rejection rate in production of the devices is reduced.
After the epitactic production of the devices, known of itself, and their
subsequent provision with contacts, the devices are then separated from
each other in particular by sawing, with the growth substrate being
removed by selective etching before or even after separation. Despite this
improvement, the rejection rate is still high, so that these devices are
still very expensive. Moreover, manufacture of a diamond layer with such
edges is technologically difficult and hence is expensive as well.
The goal of the invention is to improve the composite structure so that the
total costs for microelectronic devices made with the aid of the composite
structure are reduced, with the best possible device quality.
This goal is achieved according to the present invention. Despite the high
temperature that endangers devices when polycrystalline diamond is
deposited on devices that are already finished and produced directly in
known fashion, the rejection rate is reduced. Thus, the total costs of
producing the devices is reduced. Moreover, the method of manufacturing
the devices is known and can be accomplished at very low cost; the same
applies to deposition of the diamond layer, as attention no longer needs
be paid to its structure (edges). In particular, the devices can continue
to be separated by sawing up the composite structure, and the diamond
layer applied to most of the devices is still usable after sawing.
Other objects, advantages and novel features of the present invention will
become apparent from the following detailed description of the invention
when considered in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be explained on the basis of the embodiments shown in
the figures.
FIG. 1 shows a growth substrate with several devices and a diamond layer
deposited thereon and formed as individual diamond islands.
FIG. 2 shows a portion of a section through a device with a diamond layer,
made of diamond regions, located thereon.
FIG. 3 is a diagram of a CVD system for depositing diamond on substrates.
FIG. 4 is a detailed drawing of a substrate holder.
FIG. 5 is a detailed drawing of a nozzle for the CVD method by arcjet.
FIG. 6 is a detailed drawing of a cover.
FIG. 7 shows the application of an immunization layer to a portion of the
substrate surface.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
FIG. 1 shows a composite structure 32 having several microelectronic
devices 33. Devices 33 are disposed immediately on growth substrate 35. As
can be seen in particular in FIG. 2, devices 33 are made by functionally
using the material of growth substrate 35. "Functional use" is understood
to mean that, in the area of a device 33, growth substrate 35 has for
example a buried function layer 38 which in particular has n-doped or
p-doped or intrinsic semiconductor layers.
Growth substrate 35 and the function layers 36, 37, and 38 of device 33
disposed directly thereon form a substrate 2 that is provided with a
diamond layer on its external substrate surface 6, particularly by means
of a CVD arcjet method.
Diamond layer 34 is formed of individual diamond islands spatially
separated from each other, which are deposited in the polycrystalline form
exclusively in the vicinity of devices 33. To achieve good adhesion on the
surfaces of devices 33, the diamond islands are divided in turn into
individual diamond regions that are also separated from each other. As a
result, the voltage between diamond layer 34 and the surface of device 33
below it is at least reduced.
FIG. 2 shows a portion of a section transversely to the flat side of growth
substrate 35, made in particular of largely monocrystalline silicon, of a
microelectronic device 33 according to the present invention. Device 33
has function layers 38 buried in growth substrate 35. Buried function
layers 38 may for example be n-doped or p-doped semiconductor layers or
intrinsically conducting semiconductor layers, with the doping being
carried out in the usual way, particularly by diffusion and/or ion
implantation.
Electrically insulating layers 37 are disposed on buried function layers
38, and consist for example of SiO.sub.2 or undoped diamond and are
advantageously deposited epitactically from a gas and/or liquid phase.
In the plane of the flat side of growth substrate 35, between insulation
layer 37 and buried function layers 38, traces 39 are disposed, and
preferably comprise aluminum.
Above an insulation layer 37, another function layer 36 is disposed, which
is favorably deposited in a generally known epitactic process from a gas
phase and/or a supersaturated liquid.
Individual diamond regions of diamond layer 34 are disposed above deposited
function layers 36 and also at least partially above traces 39. The
diamond regions of diamond layer 34 are separated spatially from each
other so that even after deposition of diamond layer 34, the substrate
surface 6 of substrate 2 is still open in spots. Such open areas of
substrate surface 6 are provided in particular at contact points 40 at
which device 33 is provided with electrical contacts.
FIG. 3 is a diagram of an apparatus for coating a substrate 2 with diamond
layer 34. This apparatus is a supersonic DC arcjet system. The CVD system
has a power range of between 1 and 5 kW.
Cylindrical reactor 10 (recipient) consists of stainless steel and has a
double-wall design, making possible a water cooling system connected with
the reactor by a water connection 13.
For evacuating the inside of the reactor 14, the apparatus has a pumping
system 15 provided with pressure regulation 31, with three individual
pumps. The pressure that can be reached is approximately 10.sup.-3 moar.
In embodiments, the pumps provided are one vane pump and two Roots pumps.
In addition, the apparatus has a gas supply system 16 with which the gases
needed for a plasma (e.g., argon and/or hydrogen) and the process gases
required for the diamond growth, in particular oxygen and methane, can be
fed into the inside 14 of the reactor.
To determine if the temperature of substrate 2 is above 400.degree. C., it
may be advantageous if the apparatus has a heat pyrometer.
A substrate holder 1 is located inside the preferably evacuable reactor 10,
the holder being provided to receive the pretreated and already seeded
substrate 2 in such a way that it is flush and conducts heat well. The
design of substrate holder 1 is shown in FIG. 4.
Substrate holder 1 includes a solid rotationally symmetrical block 17 that
is T-shaped in cross section and is made of copper. In the middle of the
block, a thermocouple 12 is provided preferably made of chromium/aluminum
(Cr/Al), for measuring the temperature of substrate 2. The free surface of
the larger cross section of block 17, referred to hereinbelow as substrate
side 3, faces substrate 2. A cooling body 18 made of copper is placed
around block 17's thinner cross section in close contact with good heat
conduction. Cooling body 18 has channels 19 in its interior through which
fluid can flow for a coolant, especially water, said channels being
connected with a cooling system 32.
Because of the copper, which is a good heat conductor, and the internal
coolant flow, it is possible with substrate holder 1 to control the
temperature of a substrate 2 placed thereon and provided in particular
with a layer of conducting silver for example that is a good conductor of
heat during coating with diamond at temperatures below 450.degree. C.
However, with such cooling, substrate 2 at a maximum water temperature of
approximately 368 K can be kept only between approximately 400.degree. C.
and 500.degree. C. In addition the possible temperature regulation is also
limited to a range of approximately 85.degree. C.
Instead of the conducting silver, a narrow gap can also be provided between
substrate 2 and the substrate side, through which a gas is allowed to
flow, with temperature control then being performed by convection. Since
this gap is usually less than 1 mm, this case is also to be understood as
direct heat conduction in accordance with this application. However, this
is at least partially unsatisfactory for coating at lower temperatures,
like those that are required especially in the present case of diamond
coating of at least largely finished microelectronic devices 33 and in
this particular case of microelectronic devices 33 provided with traces 39
made of aluminum.
In order to improve this situation, substrate holder 1 has on its substrate
side 3 a temperature control disk 4 traversed internally (flow channels
11) by a temperature control gas stream, on which disk substrate 2 is
placed. A thermal insulating layer 20 can also be provided between
temperature control disk 4 and substrate side 3.
Since temperature control disk 4 with ribs 21 abuts at least indirectly
against substrate side 3, the heat between temperature control disk 4 and
substrate side 3 of block 17 can be conducted through contact directly
only in those areas. Between block 17 and cooling body 18, heat transfer
takes place over the entire surface.
In addition, a rib-shaped design of temperature control disk 4 is also
possible, with the temperature control gas, especially air, being
conducted through the channels 22 that are formed between substrate side 3
and temperature control disk 4.
All the possibilities and their combinations have in common the fact that
the entire removal of heat in substrate holder 1 is less than the heat
loss in a full surface system. This is advantageous because in unfavorable
cases the cooling action can be too great and the substrate temperature is
then too low.
Although the specific thermal capacity of the temperature control gas is
approximately only 25% of the specific heat capacity of water, a substrate
2 that is placed at least indirectly on temperature control disk 4 and
hence on holder surface 5 of substrate holder 1 can be kept at
temperatures below 400.degree. C. and even below 300.degree. C.
As a result, the microelectronic devices 33 are stressed only to a slight
extent, especially negligibly, during diamond coating. The lower
temperature during coating of microelectronic devices 33 with diamond
significantly lowers the rejection rate. In addition, the temperature
interval within which substrate 2 can be temperature controlled is
increased.
A jet 23 is located opposite substrate 2 and is suitable for producing a
gas jet for coating substrate 2 with diamond. Such jets 23 were originally
developed for space flight, but in this application the dissociation of
the carrier gas from hydrogen represents a high loss. On the other hand,
the degree of dissociation of the carrier gas that is referred to as
process or precursor gas for example in the epitaxis of diamond from the
gas phase is significant.
The design of jet 23 is shown in FIG. 5. Jet 23 has a cathode 9 that is
located axially and centrally and is axially movable, the cathode having a
melting point of 3410.degree. C. and consisting of a tungsten alloy
containing 2% thorium. Cathode 9 is made in the form of a jet needle and
simultaneously functions as a sealing needle for jet opening 24.
Approximately in the middle of cathode 9, a gas inlet opening 25 is
provided for one or more gases, especially hydrogen, that later form a
plasma. An anode 8 is located at the outlet side area of jet 23. The
actual jet opening 24 is formed by an insert, the so-called constrictor 26
which belongs to anode 8. In the vicinity of constrictor 26, the
electrical discharge arc required for plasma formation is stabilized.
In the vicinity of the needle tip of cathode 9, in other words at the
closure of jet opening 24, an injector disk 27 is provided, arranged
concentrically with respect to cathode 9, for one or more gases of the
plasma, while outside jet opening 24 an injector disk 28 for process gas
(CH.sub.4 and O.sub.2) is located.
Anode 8 of the jet is made dome-shaped and arranged concentrically in the
area of the jet opening around cathode 9. Anode 8 absorbs the electrode
current and is exposed to strong thermal stresses. In order to reduce the
stresses, the contact area of anode 8 is sharply enlarged, so that the
pressure gradient in the expansion range increases. The high pressure
gradient increases the free path length and the contact area of anode 8 is
smeared.
Between the inlet and outlet of jet 24 the pressure drops from
approximately 1 bar to approximately 0.3 mbar, in other words between 3
and 4 decades. The plasma gas formed is sharply depressurized, so that the
plasma which is originally at a temperature of approximately 20,000 to
30,000 K is cooled to 5000 K. The static pressure at the jet outlet is
greater than the pressure in the reactor. The jet speed reaches
approximately one to three times the speed of sound as a result of the
sharp expansion of the plasma.
In the following, the function of jet 23, in other words the arcjet, will
be discussed briefly. An electrical field is built up in jet 23 between
cathode 9 and anode 8. The electrons coming from cathode 9 are sharply
accelerated. A portion of the kinetic energy of the electrons is delivered
through impact processes to the gas that later forms the plasma,
hereinafter referred to simply as hydrogen, with the hydrogen ionizing and
dissociating. In the middle of the needle-shaped cathode 9 the hydrogen is
introduced tangentially to cathode 9, with the hydrogen being given a
twist. As a result of the convergent geometry of the gas chamber between
anode 8 and the housing surrounding it, the hydrogen is accelerated and a
short distance before constrictor 26 comes in contact with the discharge
arc from the cathode tip. The relatively high pressure in the vicinity of
constrictor 26 produces a high impact rate and hence a good thermal
contact between the electrodes of the discharge arc and the hydrogen and
to the formation of a plasma. Downstream from jet 23, the plasma beam
expands so that its energy density decreases.
The process or precursor gas is introduced into the rapidly flowing plasma
from the front, in other words the outflow side injector disk 28, with the
energy of the gas being increased in the plasma and conducted away from
the gas stream in the direction of substrate 2, where it is deposited in
the form of diamond.
Between jet 23 and substrate surface 6 to be coated, a cover 7 is provided,
shown more exactly in FIG. 6. Plate-shaped cover 7 has an approximately
triangular shape. Cover 7 is pivotably secured to a pivot axis 29 that is
aligned parallel to the surface normal of substrate 2. At one marginal
area, cover 7 has a preferably circular coating opening 30 which is
adapted to the shape of the substrate. In the other area, which has the
same distance from the pivot axis as the coating opening, the cover is
made continuous up to the coating opening 30, with the diameter of coating
opening 30 preferably being approximately the same as the diameter of
substrate 2, more preferably slightly larger.
Cover 7 protects the seeded substrate surface 6 of substrate 2 from the
ignition of the plasma and is not removed until the plasma and/or the gas
stream that performs the coating action and is made of precursor material
has stabilized once more. The covering time following ignition of the
plasma is between 5 and 30 minutes and preferably between 10 and 20
minutes and more preferably about 15 minutes. Advantageously, cover 7 is
cooled at least during the coverage of substrate 2. Cooling is
advantageously performed using a liquid coolant, preferably water, that
flows through channels located in the cover.
It is also advantageous, before igniting the plasma, to first allow an
inert gas, preferably a noble gas, preferably argon (Ar), to flow as a gas
between an anode and a cathode, to ignite the argon, and to produce an
argon plasma. During a transitional phase, hydrogen is introduced into the
Ar plasma, ignited, and used as a plasma material, with the argon being
removed after the transitional phase.
In this procedure, the process gas used as the precursor material is
introduced early with the H.sub.2, especially as soon as possible after
the transitional phase, and it is especially advisable at lower
temperatures to add oxygen (O.sub.2) together with the process gas used as
the precursor material.
We will now describe the method for producing a composite structure
according to the invention. First, the purified growth substrate 35,
pretreated in the usual fashion, is placed in reactor 10, and reactor 10
is evacuated. After evacuation, with the aid of the growth substrate 35,
several microelectronic devices are produced in terms of their layered
structure using an epitactic method in known fashion. As mentioned above,
growth substrate 35 and the functional layers 36, 37, and 38 of the device
33 located directly on it form substrate 2, which will be provided on its
external substrate surface 6 with diamond layer 34.
Following the production of substrate 2, an immunization layer 41 is
applied areawise to the substrate surface 6 away from growth substrate 35
or by means of a lithographic method, for example a photo-resist AZ 4533
with a layer of 1 to 5 .mu.m is applied which is baked at approximately
80.degree. C. In the area of the immunization layer, the seeding of
substrate surface 6 is prevented or at least made more difficult. The
concept of making more difficult in this context means that following
seeding, the seed density in these areas is too low to form a closed
diamond deposition.
Following the application of the immunization layer, the seeding of the
remaining free substrate surface 6 proceeds. The substrate surface is
preferably seeded mechanically and/or with the aid of ultrasound.
During ultrasonic seeding, the substrate is placed in a tank with a
diamond-water suspension and irradiated with ultrasound. The substrate
surface 6 is preferably provided in the area outside the immunization
layer with the growth seeds.
In mechanical seeding, a sludge made of isopropanol and diamond powder is
applied and the grains of the diamond powder are ground or polished into
the substrate surface. Here again, substrate surface 6 is preferably
provided outside the immunization layer with the growth seeds.
Following seeding, the immunization layer is removed and diamond layer 34,
as described above, can be applied. In particular the immunization layer
can be removed during or even before the deposition of diamond layer 34,
for example by dissolution in acetone, ashing, in oxygen plasma, by plasma
etching, or purely by heat.
Instead of the above procedure for seeding, other types of selective
seeding are possible. Thus, it is particularly advantageous to apply a
photo-resist at the spots where the diamond later will be located later,
the photo-resist being mixed with growth seeds for the diamond layer.
Hence, suppression of seeding does not take place but it is determined by
the photo-resist.
In the following table, the experimental parameters are listed for various
substrate materials and their results. All substrates are pretreated in
comparable fashion. The substrates are purified and seeded in accordance
with the disclosed methods; the seed density and the size of the growth
seeds are comparable. The following terms are used in the table:
No.: Sample number;
Sub.: Material of substrate, with the microelectronic device being a MOSFET
in SI/SiO.sub.2 technology, which was fully functional before and after
coating;
CH.sub.4 /H.sub.4 : Ratio of methane to hydrogen in percent (%);
O.sub.2 /CH.sub.4 : Ratio of oxygen to methane (%);
H.sub.2 flow: Gas flow of hydrogen in [slm];
I.sub.D : Current flow in jet between anode and cathode in amperes (A);
T.sub.S : Substrate temperature during diamond deposition in (.degree. C.);
P.sub.D : Average power in arcjet in (kW);
t.sub.w : Process duration in (min);
d.sub.s : Average layer thickness of diamond layer in (.mu.m);
v.sub.s : Growth rate or speed in (.mu.m/h); and
Adhesion: Adhesion of diamond layer to the respective substrate.
__________________________________________________________________________
A246
micro-
No. A214 A162 A163 A212 A252 electronic A219
Sub. Si Al Al Al Al device WC-Co
__________________________________________________________________________
CH.sub.4 /H.sub.4
0.29 0.28
0.28 0.29
0.30 0.3 0.3
O.sub.2 /CH.sub.4 13 15 15 13 12 12 15
H.sub.2 flow 15.6 14 14 15.6 15.6 14
I.sub.D 20 15 15 20 22 22 15
T.sub.S 360 405 405 360 360 380 280
P.sub.D 2.48 1.78 1.78 2.4 2.8 2.75 1.8
t.sub.W 135 180 120 100 60 350 120
d.sub.S 1.3 2.1 1.5 1.8 0.5 0.8 1.6
v.sub.S 0.74 0.7 .075 1.08 0.5 1.2 0.8
adhesion good good good good good good good
__________________________________________________________________________
As is clear from the table, high growth speeds and rates could be achieved
on all substrates that are approximately a decade higher by comparison
with the growth speeds and rates known at these temperatures.
All of the samples listed show good adhesion of the diamond layer to the
substrate. The adhesion was determined with a so-called Scotch Tape Test
(ST test). In this test, the diamond layer was covered by a strip of
adhesive tape (brand name Tesa-Film). If the diamond layer does not come
loose from the substrate when the adhesive tape is pulled off, the
adhesion is considered sufficient.
The foregoing disclosure has been set forth merely to illustrate the
invention and is not intended to be limiting. Since modifications of the
disclosed embodiments incorporating the spirit and substance of the
invention may occur to persons skilled in the art, the invention should be
construed to include everything within the scope of the appended claims
and equivalents thereof.
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